Bi-metallic circuit breaker snap reed



July 14, 1964 H. EGE 3,141,080

l BI-METALLIC CIRCUIT BREAKER SNAP REED Filed April 7, 1961 INV EN TOR fi/i/vs [5255 ATTORNEYS United States Patent Illinois Filed Apr. 7, 1961, Ser. No. 101,461 1 Claim. (Cl. 200-113) The invention relates to a new and improved form of bi-metallic reed for use in a circuit breaker device. More specifically, the invention is directed to a new and improved bi-metallic reed which is of unique design and configuration and which is particularly adapted for use in circuits of low amperage with positive, fast, flutterless snap action.

Circuit breaker devices including a bi-metallic reed as a part thereof are subject to many uses under widely variable conditions. By way of example, reed-type circuit breakers are used in battery chargers to protect against over-heating of the battery being charged, in trucks and other vehicles to protect against shorts in the various electrical circuits, and in hot air hand driers, etc. The reeds are formed from diverse metals which are laminated together under pressure. Such metals include brass and steel with the brass acting faster than the steel in response to heat developed as a result of current flowing through the reed. The response to heat-build-up in the reed is controlled by the particular configuration or design of the reed which is often based on the controlled provision of sized areas through which the current flows. The reed is tensioned in some respect, usually by dishing and/or by dimpling, to provide the same with a reversible. concave-convex shape. Thus with the widely variable use of circuit breaker bi-metallic reeds, it is often the case that for given circuit operating conditions the reed used must be specifically designed in order to function properly in the specific environment.

It is an object of the present invention to provide a new and improved bi-metallic reed for use in a circuit breaker device, the reed being of special design and con figuration particularly adapting the same for response to low amperages.

A further object is to provide a new and improved bi-metallic reed for use in a circuit breaker device, the reed being of unique design and configuration particularly adapting the same for efficient response to low amperages, and further being of generally uncomplicated structure permitting economical manufacture thereof.

Other objects not specifically set forth will become apparent from the following detailed description of the invention made in conjunction with the accompanying drawing wherein:

FIG. 1 is a fragmentary perspective of a circuit breaker device having the new and improved reed of the present invention operatively mounted thereon;

FIG. 2 is a longitudinal section of the device of FIG. 1 on reduced scale taken generally along line 22 therein and illustrating the reed in side elevation;

FIG. 3 is a transverse section of the device of FIG. 1 taken generally along line 3-3 therein; and

FIG. 4 is a partly sectioned plan view taken generally along line 44 in FIG. 2.

The drawing illustrates a conventional type of circuit breaker device which, as best shown in FIGS. 2 and 3, comprises a mounting block 10 provided with a removable cover member 11. The block 10 has received therethrough a pair of vertically directed terminal studs 12 and 13 which include a reed mounting terminal head 14 and a contact head 15 both of which project upwardly from the top surface of the base 10. The outer depending ends of the studs 12 and 13 are suitably threaded 3,141,080 Patented July 14., 1964 for receiving wire leads thereon clamped between nuts 16 and other fastening means not shown.

The new and improved bi-rnetallic reed 17 of the present invention is operatively mounted above the base 10 in the interior of the cover member 11. The reed as best shown in FIGS. 1 and 4 is of generally rectangular outline and is subdivided along its major axis generally into an endmost mounting portion 18, a central snap action portion 19, and an opposite endmost contact portion 20. The reed 17 is formed from any suitable laminated metallic materials which exhibit sufiiciently different thermo-responsive properties and which are highly current conductive in order to basically respond and function in the manner which is expected with regard to known types of circuit reeds. The mounting portion 18 is provided with a centrally located aperture by means of which the reed is fixedly secured to the terminal head 14 of the stud 12. The contact portion 20 is provided with a disc-like contact member 21 on the under surface or bottom face thereof and located for flat engagement with the top surface of the contact head 15 of the terminal stud 13 when the reed is in its closed circuit position. The contact disc 21 may be formed from silver or the like and suitably welded to the contact portion of the reed.

The central snap action portion 19 of the reed 17 is provided with a pair of transversely spaced, paralleling slots 22 which extend longitudinally of the reed throughout a substantial area thereof. The slots 22 are spaced inwardly of the side margins of the reed and with each adjacent side margin, each slot cooperatively defines therebetween a relatively thin, longitudinally extending ribbon-like portion 23. The central snap action area between the slots 22 is suitably treated during manufacture of the reed to be tensioned out of the normally flat plane of the reed blank to impart to the reed the basic snap action functioning. This intermediate area as best shown in FIG. 1 is drawn upwardly along a line 24 extending transversely thereof and generally centrally thereof. The line 24 actually diagrammatically illustrates the upward drawing or tensioning of the central area between the slots 22, it being understood that the actual drawing need not necessarily occur on a single thin line, although preferably it is limited to a very thin transversely extending area.

The drawing of the central area between the slots 22 is brought about by the use of a suitable die member with the reed 17 in the initial flat blank form. of the reed. The die member may include a reed supporting surface which is centrally depressed in shallow V-shape and a cooperating die member or punch which is of projecting shallow V-shape. Force is applied through one of the die members during the closing of the die on the central portion of the reed and this portion is drawn or tensioned upwardly out of the plane of the reed to impart to the reed a generally concave-convex over-all shape. The upward drawing of the center portion of the reed along the transverse line 24, does not extend outwardly beyond the slots 22 into the ribbon-like portions 23.

In order to provide the reed 17 with improved response to low amperages, the ribbon-like portions 23 located between the slots 22 and the adjacent side margins of the reed are each off-set from the original flat plane of the reed in a direction opposite to that in which the center area is drawn or tensioned. The downward off-setting of the ribbon-like portions 23 as illustrated in FIG. 1 exists between lines 25 which extend transversely across the ribbon-like portions and are located inwardly from the ends of the adjacent slots 22. As is shown in FIG. 2, the downward off-setting of the ribbon-like portions 23 provides the same with a top surface con cave configuration and a bottom surface convex configuration. The center area which is tensioned upwardly along the line 24 is actually provided with a configuration conforming to an inverted shallow V as viewed.

The downward oft-setting of the ribbon-like portions 23 provides for strong positive contact between the disc 21 and the contact head 15. During closed circuit operation, the current will flow principally along the broken lines 26 shown in FIG. 4 with the result that the central area between the slots 22 will become heated. Upon reaching the prescribed temperature, the central area will reverse itself in configuration generally along the line 24 and the reed 17 will assume a reverse dished shape of the nature shown in broken lines in FIGv 1. The configuration of the central area between the slots 22 is such that a positive snap action will occur resulting in fast separation of the disc 21 out of contact with the terminal head 15. Upward dishing of the reed 17 will place the off-set areas of the ribbon-like portions 23 under greater tension and when the center area cools off to an extent that the reed will snap back into circuit closing relation, the oppositely off-set ribbon-like portions 23 will function to provide for immediate positive closing of the circuit.

With the arrangement described, it Will be appreciated that the upwardly drawn central area between the slots 22 cooperatively functions with the downwardly off-set ribbon-like portions 23 to provide counterbalancing snap action forces in response to temperature variations in the reed 17. In this regard there is no single area of the reed which is solely relied upon for positive snap action in opposite directions. The oppositely tensioned or drawn areas of the reed 17 arranged in the manner described provide a delicate counterbalancing effect and cooperate with one another during snap action operation of the reed in opposite directions. This apparently somewhat complicated principle of operation is readily attained in a very simple uncomplicated reed design. This design is such that a flat blank of laminated bimetals may be appropriately slotted and tensioned in the manner described in a single die operation. Once the areas are formed to function in the manner described, the reed is ready for immediate use. The die members used are of uncomplicated design and do not include sharp or highly pointed portions which are subject to substantial wear.

The reed design described provides for sensitive positive snap action without fluttering. The reed is particularly adapted for use in circuits handling low amperages such as on the order of S and 6 amps. In this respect, it has been found that the reed 17 has particular utility in a range from about 4 to 20 amps.

Obviously certain modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

I claim:

A bi-metallic reed for use in a circuit breaker, said reed being of generally rectangular shape and comprising an end mounting portion, an opposite end' contact portion, and a central snap action portion, said snap action portion being defined by a pair of transversely spaced paralleling slots extending longitudinally of said reed adjacent to opposite side margins thereof, the central reed area between said slots being longitudinally tensioned by having been drawn in a direction perpendicular to the plane of said reed along a transverse line extending across said area from one slot to the other centrally of said area and providing said reed with a central dished shape, said slots defining with said side margins relatively thin longitudinally extending ribbonlike portions, each of said ribbon-like portions between opposite ends thereof being arcuately tensioned in olfsetting relation from the plane of said reed in a direction opposite to that in which said central reed area is tensioned, said offsetting relation defining concave-convex areas extending continuously substantially the full length of said ribbon-like portions and terminating in transverse line margins inwardly of opposite ends of said slots.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,775 Mottlau May 26, 1936 2,825,960 Protz Mar. 11, 1958 2,901,574 Raab Aug. 25, 1959 and 

